Spectrum around 60 GHz has attracted interest in connection with communication systems. For example, 60 GHz communication may facilitate a large communication bandwidth and higher data rates relative to lower frequencies of operation (e.g., WiFi). Also, the shorter wavelength in 60 GHz based systems allows for small antenna dimensions that enable multiple antenna systems, such as phased arrays.
The 60 GHz antenna form factor is on the order of millimeters, which requires advanced integration techniques for packaging. Routing signals from a chipset source to an antenna is also problematic. There may also be competing requirements between the antenna and the support circuitry. For example, the antenna may need a substrate with low permittivity and high relative thickness to obtain the greatest efficiency, a wide bandwidth, an undisturbed radiation pattern, and less coupling to other components. Conversely, the radio frequency (RF) components may require thin materials with high permittivity for compactness, better signal transmission, and better thermal dissipation.
There are various types of antennas. In a 60 GHz based system, it may be beneficial to have antennas that are omnidirectional. A typical example is a printed planar monopole antenna fed with a microstrip transmission line. However, since the wavelength is short, at 60 GHz for an off package antenna, the microstrip line length could be on the order of a wavelength. Then, if the transmission line is unbalanced, strong radiation may come from the transmission line itself.
A monopole antenna may suffer from a strong current balancing problem. Usually, a balanced feed (Balun) needs to be designed to ensure that the distribution of current in the ground and the microstrip transmission line do not cause radiation problems.